Distance Dependent Plasmonic Coupling in Linear Nanoparticle Cluster

Herein we combined the e-beam lithography and nanoparticle self-assembly methods to prepare single-line linear nanoparticle clusters. We measured the far-field spectrum under darkfield microscopy and observed the continuous red shift of the peak wavelength with increasing cluster size which matches satisfactorily with the reported simulations results.We found that the wavelength could be tuned over a spectral range of 300nm. For clusters of 6 nanoparticles or above, we did not observe a systematic additional red shift. We also found that control over the NP surface allowed a systematic variation of the gap width on length scales below the resolution of e-beam lithography. The linear NP cluster structures show very strong polarization dependency yet wavelength tunability over a large range. Considering the chemical and photostability of the noble metal particles, the reported structures facilitate the realization of nano-optical devices, especially polarization switchable devices. The wavelength of interest can be well tuned from visible to near IR. The manipulation of cluster size and gap used in this study could also lead to advancement of SERS sensing technology and fluorescence enhancement.